Some large companies, such as credit card companies and telephone companies, use large-scale relational database systems to store many millions of records per day, where each record is retained in a database on a direct access storage device for a period of time, after which the records are removed from the database. Such large-scale use might require terabytes of direct access storage to support ongoing queries. However, most queries require access to only a very small fraction of the entire database, with many records never being accessed at all during their retention period.